1. Field of the Invention
This invention relates to bulked polypropylene fibers which are readily dyed by cationic, acid, or disperse dyestuffs. More specifically, it relates to bulked polypropylene fibers which have been spun from polypropylene that has been modified by blending with a dye receptor comprising 1) a copolymer of nylon 6,6 and substantially equimolar amounts of hexamethylenediamine and the alkali salt of 5-sulfoisophthalic acid or its derivatives, or 2) a basic copolyamide that is a reaction product of N-(2-aminoethyl)piperazine, adipic acid, hexamethylene diamine, and optionally, .epsilon.-caprolactam. The dye rate of the bulked fibers of the current invention is significantly improved over unbulked fibers and is increased by post dry heat treatment following bulking.
2. Prior Art
The term "bulked" is used herein to describe yarns that have been textured using a jet- or jet-screen texturing method in which a heated turbulent fluid is used to generate bulk. Breen & Lauterbach, U.S. Pat. No. 3,186,155, discloses an example of a jet-bulking process which involves exposing a bundle of filaments to a jet of rapidly moving turbulent fluid to generate bulk. Nylon 6,6,nylon 6, and polyethylene terephthalate yarns were found to exhibit faster dyeing rates when subjected to the jet-bulking process. Bulked polypropylene yarns are also disclosed, however they were formed from unmodified polymer which is not dyeable by acid or cationic dyestuffs. Miller, Clarkson, & Cesare in U.S. Pat. No. 3,686,848 disclose textured yarns spun from polypropylene modified with up to 10% poly(vinylpyridine). The effect of the texturing process on the dye rate of fibers spun from these compositions was not examined.
Polyolefins, particularly polypropylene, are used widely in the production of fibers for a variety of textile applications, including carpets. One of the major limitations of this class of polymers is that they are nonpolar and lack affinity for dye molecules, and therefore are not dyeable by conventional means. The current method of choice for commercial dyeing of polypropylene fibers is solution dyeing, a method whereby a pigment is added to the polymer melt during the spinning process. Solution-dyed polypropylene fibers have the advantages of a high degree of fastness, resistance to staining, and in many instances, lower cost than fibers made from other resins. However, solution-dyed fibers have the disadvantage that they are available from fiber producers in a limited number of colors and large inventories must be maintained, resulting in high inventory costs. Solution-dyed fibers also have the disadvantage of lack of printability, which further limits their flexibility. Polypropylene yarns which are dyeable using conventional methods will have the advantage of giving textile manufacturers increased styling flexibility over currently available solution-dyed fibers.
Suggestions have been made in the art for improving the dyeability of polypropylene by attaching dye-receptive groups to the polymer by copolymerization or grafting, or by blending with modifying polymers which contain dye-receptive groups. These methods have resulted in only moderate improvements in dyeability and have been unacceptable due to additional problems of nonuniformity, caused by incompatibility of the additives with polypropylene, or high cost.
Alliot-Lugaz & Allard, U.S. Pat. No. 3,328,484, disclose ternary polypropylene compositions for the manufacture of unbulked filaments comprising a major proportion of polypropylene and a minor proportion of a mixture of (i) a synthetic, linear polyamide and (ii) not more than an equal weight of a synthetic linear sulfonated copolyamide. These compositions are homogenous and are dyeable by basic, acidic, metallized and disperse dyes. The above-referenced patent also discloses binary compositions having an affinity for basic dyes comprising a major proportion of polypropylene and a minor proportion of a sulfonated polyamide and describes the compositions as being difficult to extrude.
Earle, et al., U.S. Pat. No. 3,433,853, disclose compositions for the manufacture of unbulked filaments comprising a major amount of a polyolefin and a minor amount of a basic polyamide which is a copolymer of an aliphatic dicarboxylic acid and a polyamine containing no more than two primary amino groups and one or more tertiary amino groups, where up to 60% of the polyamine may be replaced by a diamine. Oldham, U.S. Pat. No. 3,465,060, discloses compositions for the manufacture of unbulked filaments comprising a major proportion of a polyolefin containing a minor amount of a basic polyamide, where the polyamide is the reaction product of one or more dicarboxylic acids with a polyamine having at least 3 amino groups, at least one of which is secondary or tertiary, and a lactam containing 6-12 carbon atoms. Part of the polyamine may be replaced by diamine. These compositions provide olefin polymers with improved acid dyeability.